Duolingo

Duolingo ( DEW-oh-LING-goh) is an American educational technology company which produces language-learning apps and provides language certification.
On its main app users can practice vocabulary, grammar, and pronunciation using spaced repetition. Duolingo offers over 100 total courses across 41 distinct languages, from Spanish, French, German and Japanese to Navajo and Yiddish. It also includes a small variety of constructed languages. The company uses a freemium model with over 500 million registered users. Duolingo offers a premium service which eliminates advertising and offers more features.
Duolingo also offers Duolingo English Test certification program and a literacy app for children: Duolingo ABC.